Functionalization of single-walled (n,0) carbon and boron nitride nanotubes by carbonyl derivatives (n = 5, 6): a DFT study

By using density functional theory calculations, the chemical functionalization of finite-sized (5,0) and (6,0) carbon nanotubes (CNTs) and boron nitride nanotubes (BNNTs) by different carbonyl derivatives –COX (X = H, CH3, OCH3, OH, and NH2) is studied in terms of geometrical and electronic structure properties. Also, the benefits of local reactivity descriptors is studied to characterize the reactive sites of the external surface of the tubes. These local reactivity descriptors include the electrostatic potential VS(r) and average local ionization energy ĪS(r) on the surfaces of these nanotubes. The estimated ĪS(r) values show that the functionalized CNTs tend to activate the surface toward electrophilic/radical attack. Results show that the chemical functionalization of CNTs leads to the reduction of VS(r) values and therefore enhances the surface reactivity. On the other hand, BNNTs resist chemical functionalization due to the negligible decrease in the VS,min and ĪS,min values. Generally, in contrast to BNNTs, the chemical functionalization of CNTs can considerably improve their surface reactivity. To verify the surface reactivity pattern based on the chosen reactivity descriptors, the reaction energies for the interaction of an H + ion or hydrogen radical with external surface of the functionalized CNTs and BNNTs are calculated. A general feature of all studied systems is that stronger potentials are associated with regions of higher curvature.

A theoretical study on surface reactivity of fluorinated (n,0) and (n,n) carbon nanotubes (n = 3–6)

Density functional theory calculations are performed to investigate the surface reactivity of pristine as well as fluorine-terminated zigzag (n,0) and armchair (n,n) carbon nanotubes (n = 3–6). The properties determined include the electrostatic potential V(r) and average local ionization energy Ī(r) on the surfaces of the investigated tubes. A general feature of all of the systems studied is that stronger potentials are associated with regions of higher curvature. The results indicate that both V(r) and Ī(r) detect the effects of fluorine-terminated regions in which significant effects are observed for those atoms in the vicinity of the fluorine-terminated regions. Comparison with the Ī(r) of the pristine nanotube indicates correctly that in the fluorine-terminated models, the fluorine atoms tend to deactivate the surface toward electrophilic/radical attack.